The field of integrated photonics seeks to miniaturize optical components, such as modulators, resonators, filters and waveguides, and integrate such optical components onto a single chip in the form of an optical circuit. Many researchers in the field of integrated photonics hope to revolutionize optics in much the same way that miniaturization and integration of the circuits has revolutionized electronics. In the context of high performance computing, for example, optical interconnects would be advantageous in order to improve the bandwidth of communication between computational nodes in supercomputers, and potentially decrease the power consumption of such large scale computers.
In analogous manner to the microelectronics industry, the fabrication of integrated photonic circuits through lithographic, and other highly manufacturable means, seeks to: (1) reduce cost and size, (2) increase complexity, and (3) improve the overall performance of optical systems. Numerous researchers have placed a great deal of effort toward the development of high refractive index contrast (HIC) photonic circuits for their ability to further reduce component sizes and improve performance even further.
While progress has been made in the field of HIC photonic circuits toward the development of practical and low-loss waveguides, high performance filters, resonators and modulators, numerous fundamental challenges remain before widespread implementation of such photonic circuits can occur. For example, HIC photonic circuits, such as those made from silicon, are extremely sensitive to their environment.
Since the refractive index of silicon changes very rapidly with temperature due to the thermo-optic effect, it can be challenging to stabilize the resonance frequency of an optical cavity of a photonic circuit against variations in temperature. If optical cavities were used on microprocessors in order to filter and route optical data on chips, for example, large variations in the local processor temperatures during operation may detune those cavities from their intended resonant frequencies. All of these devices are notoriously temperature sensitive, as changes in both device dimension and refractive index severely impact the performance of the system. Active thermal compensation in the form of a thermal sensor, a heater and a feedback loop, has been pursued as a solution to this problem, however, this is a costly, complex and inefficient solution requiring additional power and components.